PROJECT SUMMARY/ABSTRACT We propose to renew the NIEHS Training Program in Environmental Epidemiology. This program seeks to prepare outstanding researchers in environmental epidemiology through rigorous training and research methodology. Currently in its 40th year, this program is the cornerstone of support for students working in environmental epidemiology at the Harvard T.H. Chan School of Public Health (HSPH). We have graduated over 200 professionals who are researchers, teachers, and consultants in environmental epidemiology and related disciplines. Many hold leadership positions in academia, government, and the private sector. The Program consists of two tracks: environmental epidemiology and environmental molecular epidemiology and training for both tracks is offered at the pre- and postdoctoral levels. We leverage the rich academic environment at HSPH, the Harvard teaching hospitals and other Harvard University schools such as the Graduate School of Arts and Sciences to provide numerous opportunities for cutting edge research in environmental health. We have brought together outstanding multi-disciplinary faculty mentors to provide integrated interdisciplinary experiences and have created a specialized curriculum providing a strong background in environmental health, exposure assessment, epidemiology, and biostatistics. The track in environmental molecular epidemiology offers additional coursework in molecular biology, genetics, epigenetics, etc. and opportunities to conduct research in a laboratory setting. For this funding cycle we request 6 pre- and 6 postdoctoral trainees. The predoctoral students are part of the new multidisciplinary PhD program in Population Health Sciences with a chosen field of study in environmental health or epidemiology. The PhD program is structured to be completed in 4 years with the first 2 years involved in coursework. Research credits are obtained through tutorials on current problems in epidemiology and from the completion of a doctoral thesis of substance. Postdoctoral trainees are exposed to a wide variety of interdisciplinary and integrated intellectual offerings, including didactic instruction, seminars, professional colloquia, meetings, and academic collaboration. Significant independent research for the postdoctoral fellows varies in duration depending on the scope of work, but usually is between 2 to 3 years. All trainees complete individual candidate training plans and there is ongoing evaluation of the Program. This program will continue a long history of excellence in training successful researchers in the field of environmental epidemiology at Harvard University and in furthering the mission of NIEHS.